A population of T cells has been stimulated to proliferate in response to a part

Question

A population of T cells has been stimulated to proliferate in response to a particular antigen. A sample of 2000 cells is examined microscopically, revealing that 400 of these cells are in the various stages of mitosis. Of the remaining 1600 in interphase, 700 have x amount of DNA, 400 have 2x, and the remaining 500 have amounts somewhere between x and 2x.

How many cells are in G1 phase?

How many cells are in S phase?

How many cells are in G2 phase?

What is mitotic index?

Additional analysis reveals that the G2 phase of the cell cycle lasts 2 hours. What is the total length of the cell cycle?

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Explanation / Answer

Cells which are in G1-phase has X amount of DNA -

Cells which are in G2-phase has 2X amount of DNA

Cells which are in S-phase has X-2X amount of DNA

So Number of Cells in present G1 phase is -700

So Number of Cells in present G2 phase is -400

So Number of Cells in present S phase is -500

Mitotic index is given by the number of cells going mitosis/ total number of cells.

The number of cells undergoing mitosis is the sum of cells present in - prophase, metaphase, telophase and anaphase. In the given question 400 cells are at various cell cycle stage.

So Mitotic index is 400/2000 = 1/5 0or 20% cells

G2 phase constituted around 1/6th of total cell cycle time.

1/6 = 2

So the total length of cell cycle will be 2*6 = 12 hours

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